Electric discharge device



July 28, 1936. M. 1. KAHL ELECTRIC DISCHARGE DEVICE Filed Dec. 2, 1955-INVENTOR ATTORNEY Patented July 28, 1936 Hygrade Sylvania Ccrporation,Salem,

Mass.,

a corporation of Massachusetts Application December 2, 1933, Serial No.700,644

13 Claims.

This invention relates to electric discharge devices and withparticularity to devices generally referred to as radio tubes, vacuumtubes, or the like.

An object of the invention is to provide a novel method of supportingthe electrode assembly of an electron discharge tube or the like.

Another object is to provide a novel device for resiliently supportingan electrode assembly interiorly against the wall of an enclosingenvelope or the like.

In radio tubes generally, and more especially in the modern types oftubes, it is imperative that the various electrodes of the electrodeassembly be maintained accurately in predetermined spatial relations,both with respect to one another and also with respect to the wall ofthe enclosing envelope which is usually provided with an external orinternal shield. Socalled unitary mounts or electrode assemblies havehitherto been provided wherein the electrodes are interlocked by meansof insulating spacers or the like, and the electrodes after being thusassembled are supported from the press of the tube envelope. While suchtubes are capable of maintaining their inter-electrode spacings,nevertheless the entire weight of the electrode assembly must be borneby the press and the various wires sealed therein, the upper end of theassembly being usually free. Under certain conditions such as excessiveexternal vibrations, the electrode assembly tends to sway or vibratearound the press support wires, so that the press adjacent these wiresmay crack, or one or more of the seal-ins may become defective. At thesame time this vibration changes the electrostatic relation to theshield. If the vibration is not sufficient to destroy the seal, it mayresult in changes in the geometric configuration of the discharge spaceWithin the tube, by causing the assembly to vary its position withrespect to the tube walls. This vibration usually results in so-calledmicrophonic disturbances in the output of the tube when the latter is inuse.

Accordingly, one of the principal objects of this invention is toprovide a radio tube, lamp or similar device, wherein the filament orelectrode assembly is supported both from the press as well as from theupper end of the envelope, whereby variations in the characteristics ofthe tube are substantially prevented even when the tube is subjected toheavy jars or vibrations.

Another object of the invention is to provide a so-calledsingle-presstube with means for supporting the electrode assembly against tiltingmovement with respect to the press without at the same time materiallyincreasing the assembly cost or assembly time.

A feature of the invention relates to a radio 5 tube of the so-calleddome envelope type in conjunction with a novel form of spacer forinsulatingly supporting the electrode assembly within the dome.

A further feature relates to a novel form of 10 dome spacer for radiotubes, the spacer being designed and proportioned so as to be deformableat its ends whereby it automatically conforms itself to different sizesand shapes of domes. 1-5

A further feature pertains to the novel manner of supporting a domespacer from the electrode assembly of a radio tube.

A still further feature relates to improvements in so-calledunitary-assembly tubes, whereby 20 the cost of manufacture is reduced,while the reliability and accuracy of performance under varied operatingconditions are materially increased.

Other features and advantages not specifi- 25 cally enumerated will beapparent after a con sideration of the following descriptions and theappended claims.

While the invention will be disclosed herein as embodied in specificforms, it will be understood that the invention is not limited thereto,but is capable of embodiment in tubes, lamps and similar devices ofdifferent shapes and sizes.

According to the drawing, Fig. 1 is a front elevational view, partly insection, of a radio tube 35 embodying features of the invention;

Fig. 2 is an enlarged side view of the upper end of the tube shown inFig. 1;

Fig. 3 is a sectional view of Fig. 1, taken along the line 3-3 thereof;40

Fig. 4 is a detail view of one of the spacers according to theinvention;

Fig. 5 is a sectional view of Fig. 4, taken along the line 5-5 thereof;

Fig. 6 is a view of a modified form of spacer; 45

Fig. 7 is a sectional view of the spacer of Fig. 6 taken along line llthereof; 7

Figs. 8 and 9 are detail views of a modification of the spacer of Figs.1 to 7.

Referring more particularly to Figs. 1 and 2, 50 the numeral l indicatesan enclosing envelope of glass or other suitable material such as ordinarily employed in radio tubes, lamps, etc. Envelope I is providedwith a re-entrant stem 2 which terminates in the usual press 3, where 55in are sealed the various lead-in and support Wires 4 to H inclusive.The envelope I has fastened to its lower end the conventional base I2carrying the usual contact prongs l3. Envelope I terminates at its upperend in a substantially cylindrical dome-shaped portion M which carriesthe metallic contact cap i5, it being understood of course, that theenvelope is hermetically sealed and exhausted in accordance withstandard radio tube procedure, although as will be apparent from thefollowing descriptions, the invention is not limited to so-called highvacuum tubes, but may be equally well embodied in so-called gas or vaportubes. Attached to the wires 5 and i0 is a metallic electrode I6rectangular in crosssection and having its upper end preferably closed,except for a small perforation for the passage of the cathode, as willbe described hereinbelow. It will be understood, of course, thatelectrode It may be cylindrical or other suitable shape, Fastened towire 6 is a metallic strip whicl'iatits unfastened end is in the form ofa cylindrical ring. A similar member i8 is fastened to wire 9, and asshown, the ring portions l8 and 20 arein vertical axial alignment.

Supported on the wires 4 and is a plate electrode2l consisting of a pairof metallic members having their median portions pressed tosemi-cylindrical form. One of the plate members may be provided with aplurality of small perforations 22, in its lateral fiat portions, andthe other plate member may be provided with a corresponding plurality ofstruck-up lugs 25 whereby the 'two plate members may be rigidly lockedtogether as a unit to define a central cylindrical electrode space 26.The outer lateral edges of the plate members surround the wires 4 and Hto which they may be fastened as by welding or the like. Preferably,although not necessarily, thesurface 'of the plate members is carbonizedfor purposes well known in the radio tube art. Preferably, the platemembers are mounted so that the'cylindrical electrode space 26 is invertical axial alignment with the ring electrodes l8 and 20. Positionedbetween the electrode 2| and the electrode |6 isa strip 21 of insulatingmaterial such as lava, mica or the like, provided with a centralperforation through which passes the lower end of the indirectly heatedcathode sleeve 28;andalso with sets of lateral perforations to receivethe plate support wires 4 and H, and'the support wires 29 and 30 for thehelically wound grid 3|. The wires 4 and i! may be providedwith suitablelugs or projections to prevent the strip 21 moving vertically. Asshownin the drawing, the cathode comprises the usual hollow metallicsleeve'28 which is provided on its external surface with an an electronemissive coating; Passing interiorly through the sleeve 28 is a filament32 which may be in the form of an inverted V, provided with a coating ofa suitable refractory insulating material as disclosed in PatentNo.1,950,456. If desired, although not necessarily, the bight of thefilament may be held between the pinched end of the sleeve 28. Or, ifdesired, the end of the sleeve may be left unpinched and the filamentsupported in any manner well known in the art and insulated fromthesleeve 28. An insulator strip 33 similar to strip 2'! is provided at theupper end of the electrode 2| and is held in place by suitable lugs (notshown), welded orotherwise fastened to the wires 4 and H. As shown inFig. 1, the filament heater for the upper cathode 28 extends downwardlythrough the ringelectrodes l8 and 28 and the free ends of the filamentare welded to the filament lead-in and support wires 1 and 8. Thuselectrodes I8 and 20 may serve as diode anodes to the lower end of thecathode and electrode l8 may serve as a shielding electrode to shieldelectrodes l8, l9 and 20 from electrode 2|. Preferably also electrode 2|is electrically connected to the sleeve 28 as shown.

As will be evident from the foregoing, the greater part of the weight ofthe electrode assembly is distributed towards the upper end of the mainsupport wires 4 and H, and thus at a relatively great distance from theedge of the press 3. In order to prevent the electrode assembly tiltingabout the seal-in points in the press, there are provided between theupper end of the electrode assembly and the wall of the dome-shapedportion Hi, what may be termed resilient spacers. Ordinary shock take-updevices such as rubber, springs, etc., are entirely unsuitable for thispurpose. Further, since there may exist differences in internal diameterof the envelope dome, ordinary rigid spacer members are impracticablefor large scale production. Accordingly, there is disclosed in Figs. 1to 5 a novel 25 form of spacer that possesses the following advantageousfeatures: 7

(1) Low heat conductivity;

(2) -M-inimum gas absorption;

(3) Sufficient rigidity to support the electrode assembly against heavyjars while having sufficient edge deformability to automaticallyaccommodate the pad to varying internal diameters and shapes of dome.

As shown in Figs. -1 to 5 inclusive, the spacer is in the form of asheet or strip 35 of micaror other similar insulating material, ofsufficient thinness at its edges 36, 31 so that the edge portions can beslightly rounded or deformed, as shown in Figs. 3 and 6, to conform tothe curvature of the dome Hi. It will be also understood that the micaor other insulating strip used for this purpose has sufficientresiliency or flexibility that the rounding of the edges resulting fromengagementwith the dome, does not permanently deform the mica. It hasbeen found that ordinary methods of fastening mica as by cement,rivets,"et c., are unsuitable for use in spacers as described.Accordingly, the mica sheet 35 is provided with a metallic strap 38 ofnickel or other suitable metal. This strap serves the double purpose ofproviding a weldable attachment lug and at the same time acting as areenforcement for the central area of the mica. This latter feature isof importance since the mica may otherwise be subjected to sufiicientbending forces as to cause it to break or chip. Consequently, as shownin Figs. 2 and 4, the mica sheet 35 is pro vided with two rectangularopenings 39 and 40 through which passes the metal strap 4|. As 60 shownmore clearly in Figs. 3 and 5, the said strap is bent to substantialT-shaped formation so as tightly to grip the mica on opposite'faces, andwith the projecting ends 42 serving as lugs for welding or otherwisefastening to the sup- Pr'efer- 7 metal strap does not extend-to theedges of the mica spacer, only the median portion of the spacer isreenforced so. that the non-reenforced portions are capable ofconsiderable deformation without danger of breaking or cracking.Furthermore, the mica is preferably chosen of sufficient thinness as toprovide the necessary resiliency or. flexibility at its lateral edges.

The pressure against the dome thus exerted by the deformed lateral edgesof the mica, provides what may be termed cushioned resistance to motionof the electrode assembly in a direction perpendicular to the plane ofthe mica, and at the same time the lateral edges offer a similarcushioned resistance tomotion or vibration of the electrode assembly ina direction parallel to the mica. Thus there is provided a four-pointresilient support for the upper end of the electrode assembly. It willbe understood, of course, that the micas may be chosen of sufficientthickness to practically prevent motion of the assembly in responsetovibrations of small amplitude, but are capable of resilient cushioningin response to heavy jars or vibrations. Furthermore, the mica iscapable of self-conformation to the curvature of the dome and thusentirely prevents rattle between the mica and the wall of the dome.

While the drawing shows the mica spacers engaging the dome walls only atthe vertical edges, it will be understood that if desired, the saidspacers may be mounted so that their upper horizontal edges engage thedome also. It will be apparent from Fig. 4, for example, that because ofthe openings 39 and (iii, the upper edge portion of the mica is capableof limited deformation, if it is desired to. have the upper edge bearagainst the dome. ji FE Referring to Figs. 6 and 7, there is shown amodified form of spacer in which the mica sheet 44, instead of beingperforated to receive the reenforcing strap, is provided with alignedslots, around which the metal 3! is strapped. In this embodiment,therefore, a greater amount of flexible deformation along the verticaledges, as well as along the upper edge is attainable.

Figs. 8 and 9 show a still further modification of the spacer wherebygreater flexibility is provided at the edges with increased strength inthe central areas. This form of spacer is very useful where relativelygreat distances are to be spanned. As will be seen, this modificationconsists of a pair of mica discs 5'3, 5! of the same general shape asthe disc 35 (Fig. 4), and interposed between discs 50, 51 is a thirdsimilar but larger disc 52, the three discs being held together by ametal strap 53 similar to strap GI (Figs. 1 to 7) It will also beunderstood that the embodiment of Figs. 6 and 7 may be modified inaccordance with the teaching of Figs. 8 and 9 so as correspondingly toreenforce and render more flexible the embodiment of said Figs. 6 and 7.

It will be understood that the invention is not limited to a so-calledpress, but is capable of embodiment in any well-known type of tube.Accordingly, the term base as employed in the claims, is intended tocover a press or any other portion of an enclosing envelope whichcarries one or more electrodes.

If desired, the cathode sleeve 28 may terminate just above the electrode18 so that only the filament 34 extends through the electrodes l8 and20. In this latter case the portion of the filament extending throughthe electrodes i8 and 29 may be provided with an electron emissivecoating.

While the drawing shows a tube provided with a pair of oppositelydisposed mica spacers, it will be understood that a greater orlessnumber of these spacers may be provided, and that they may be attached,in the manner shown, at any other point, so long as they are positionedbetween the electrode assembly and the wall of the envelope. Variouschanges and modifications may therefore be made without departing fromthe spirit and scope of the invention.

What is claimed is:

1. In combination, an enclosing envelope having a base, an electrodewithin said envelope supported at one end from said base, a, strip ofinsulation having deformable end portions engaging the wall of saidenvelope to support said electrode at its upper end in spaced relationto said wall, and metallic means passing through said strip to reenforceit at its central portion,- said metallic means being attached to saidelectrode. a I

2. In combination, an enclosing envelope having a base, a metallicupright sealed into said base, a strip of insulation having deformableend portions engaging the wall of said envelope, a metal strap passingaround a portion of said strip to reenforce said strip at its center andto provide means for mounting said strip on said upright.

3. In combination, an enclosing envelope having a base at one end and adome at the other, a pair of metallic uprights sealed at one end intosaid base, and a pair of insulation members each having a reenforcedcentral portion and flexible end portions, said members being supportedat the upper ends of said uprights and in engagement with the inner wallof said dome.

4. The combination according to claim 3, in which each insulator memberis of mica around which passes a metal strap for reenforcement andattachment to said uprights.

5. In combination, an enclosing envelope having a base containing anelectron emitting cathode and an anode therefor, another electronemitting cathode and an anode therefor, a pair of uprights sealed intosaid base for supporting the second anode, another pair of uprightssealed into said base for supporting the first anode above the secondanode, a pair of insulator strips supported at the upper ends of thesecond-mentioned uprights, said strips having reenforced centralportions and deformable end portions adapted to engage the inner wall ofthe envelope.

6. The combination according to claim 5, in which the anodes are hollowand are supported in end-to-end relation and the insulator members areof mica.

'7. In combination an enclosing envelope having, a press, a metallicupright sealed into said press, a sheet of mica, an attachment lug forsaid sheet comprising a metal strap attached to the mica having its endsprojecting through the mica, said lug being supported by said uprightand with the edges of said sheet flexibly engaging said envelope.

8. In combination, an evacuated envelope containing a tubular cathode, aheating filament for said cathode, a hollow anode surrounding one end ofsaid filament, another hollow anode surrounding another portion of saidfilament, said other portion of said. filament being coated with anelectron emissive coating, and sheet insulator means for resilientlyspacing the first-mentioned anode from the inner wall of said envelope.

9. The combination according to claim 8, in which the insulator means isin the form of a 4 strapped mica strip attached to the first-mentionedanode.

' 10. In combination, an evacuated envelope, an electrode assemblywithin the envelope including an'upper cathode, a lower cathode, commonfilament means'forrendering both saidcathodes emissive, 'a' plurality ofelectrodes surrounding the upper cathode, a plurality of electrodessurrounding the lower cathode, and resilient insulating means carried bysaid assembly and engaging the inner wall of said envelope.

11. An anti-vibration spacer for radio tubes comprising a sheet ofinsulating material having flexible end portions, a metal strap forreenforcing the median portion of said sheet and having a portionextending at right angles to said sheet to serve as an attachment lug.

12. A spacermember"forispacing an electrode of a .radio tube from'thewall thereof comprising a sheet of mica having resilient edge por-,tions and provided with a pair of aligned openings, 'a metallic strapsurrounding said sheet between said openings to reenforce said sheetbetween said openings, the ends of said strap pass-i ing through saidopenings to serve as an attachment lug.

l 13. A spacer member for spacing an electrode of 10 a radio tubefrom'the wall thereof comprising :a pair of mica discs, one of'saiddiscs being larger than the other, anda metal strap clamping said discstogether, said strap terminating in a projection for attachingsaidspacer to asupport.

MAURICE IRWIN KAI-IL.

